In recent years, as mobile phones support multiple bands and multiple modes, multiplexers including a plurality of filters have been used. A surface acoustic wave (SAW) resonator is used for the filter of the multiplexer. The filter using a SAW resonator is used as a bandpass filter in various circuits that process radio signals in a frequency band from 45 MHz to 2 GHz typified by, for example, mobile phones. In the SAW resonator, an Interdigital Transducer (IDT) including a plurality of electrode fingers is formed on a piezoelectric substrate such as a lithium tantalate (LiTaO3) substrate or a lithium niobate (LiNbO3) substrate. The region where the electrode fingers of the IDT overlap is an overlap region. The IDT excites a Shear Horizontal (SH) wave (leaky wave), a Rayleigh wave, or a boundary acoustic wave, which is a type of surface acoustic wave. Reflectors located at both sides in the main propagation direction of an acoustic wave excited by the IDT confines the acoustic wave around the IDT. It has been known that regions with different acoustic velocities of acoustic waves are periodically arranged at regular intervals in the extension direction of the electrode fingers in the SAW resonator as disclosed in, for example, International Publication No. 2015/007319.
When regions with different acoustic velocities of acoustic waves are located at regular intervals, lateral-mode spurious is reduced. However, a large emphasis mode occurs. In the multiplexer, the emphasis mode may overlap with the passband or attenuation region of other filters.